/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.client.deployment.application;

import org.apache.flink.annotation.VisibleForTesting;
import org.apache.flink.api.common.JobID;
import org.apache.flink.api.common.JobStatus;
import org.apache.flink.api.common.time.Time;
import org.apache.flink.runtime.concurrent.ScheduledExecutor;
import org.apache.flink.runtime.dispatcher.DispatcherGateway;
import org.apache.flink.runtime.jobmaster.JobResult;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
import java.util.function.Supplier;

/**
 * Utilities for periodically polling the status of a job.
 */
class JobStatusPollingUtils {

	/**
	 * Polls the {@link JobStatus} of a job periodically and when the job has reached
	 * a terminal state, it requests its {@link JobResult}.
	 *
	 * @param dispatcherGateway the {@link DispatcherGateway} to be used for requesting the details of the job.
	 * @param jobId the id of the job
	 * @param scheduledExecutor the executor to be used to periodically request the status of the job
	 * @param rpcTimeout the timeout of the rpc
	 * @param retryPeriod the interval between two consecutive job status requests
	 * @return a future that will contain the job's {@link JobResult}.
	 */
	static CompletableFuture<JobResult> getJobResult(
			final DispatcherGateway dispatcherGateway,
			final JobID jobId,
			final ScheduledExecutor scheduledExecutor,
			final Time rpcTimeout,
			final Time retryPeriod) {

		return pollJobResultAsync(
				() -> dispatcherGateway.requestJobStatus(jobId, rpcTimeout),
				() -> dispatcherGateway.requestJobResult(jobId, rpcTimeout),
				scheduledExecutor,
				retryPeriod.toMilliseconds()
		);
	}

	@VisibleForTesting
	static CompletableFuture<JobResult> pollJobResultAsync(
			final Supplier<CompletableFuture<JobStatus>> jobStatusSupplier,
			final Supplier<CompletableFuture<JobResult>> jobResultSupplier,
			final ScheduledExecutor scheduledExecutor,
			final long retryMsTimeout) {
		return pollJobResultAsync(jobStatusSupplier, jobResultSupplier, scheduledExecutor, new CompletableFuture<>(), retryMsTimeout, 0);
	}

	private static CompletableFuture<JobResult> pollJobResultAsync(
			final Supplier<CompletableFuture<JobStatus>> jobStatusSupplier,
			final Supplier<CompletableFuture<JobResult>> jobResultSupplier,
			final ScheduledExecutor scheduledExecutor,
			final CompletableFuture<JobResult> resultFuture,
			final long retryMsTimeout,
			final long attempt) {

		jobStatusSupplier.get().whenComplete((jobStatus, throwable) -> {
			if (throwable != null) {
				resultFuture.completeExceptionally(throwable);
			} else {
				if (jobStatus.isGloballyTerminalState()) {
					jobResultSupplier.get().whenComplete((jobResult, t) -> {

						if  (t != null) {
							resultFuture.completeExceptionally(t);
						} else {
							resultFuture.complete(jobResult);
						}
					});
				} else {
					scheduledExecutor.schedule(() -> {
						pollJobResultAsync(jobStatusSupplier, jobResultSupplier, scheduledExecutor, resultFuture, retryMsTimeout, attempt + 1);
					}, retryMsTimeout, TimeUnit.MILLISECONDS);
				}
			}
		});

		return resultFuture;
	}
}
